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Dunkirk Boilers

ALH_4 Member Posts: 1,790
1) Nope. I know there are many others here who have.

2) Yes. I assume the energy use of an 87-year old building of that size is relatively high. The more you burn the more efficiency pays you back.

3) Modulating capacity refers to the "turndown ratio" of the boiler. It is the ratio of the maximum input to the minimum input. Typically this is in a 3:1 to 5:1 range for residential boilers. If you have two 4:1 boilers, you have an effective turndown of 8:1.

4) As a cost saving measure, I see absolutely no problem with installing one of each. I assume this is a high temperature copper fin tube baseboard system. However, by the time you figure the interface (piping, staging, outdoor reset, etc.) of the two types of boilers, it may cost less to use two of the modulating condensing boilers. If anything, the savings would be relatively small at the scale of your project. A single Lochinvar Knight KBN500 is another option.


  • Rich_41
    Rich_41 Member Posts: 2

    I am looking at replacing the large boiler at my 1930 eight-unit apartment building with 2 200MBH Dunkirk boilers. They have two boilers I am considering:

    a)a 90% AFUE direct vent unit and b)a 95% AFUE infinitely modulating capacity direct vent unit.

    1) Has any one used a Dunkirk or Carrier high efficiency boiler in their building(s)? (Dunkirk manufactures Carrier boiler equipment).

    2) Is it worth the extra cost (probably $1000 extra per unit) for the 95% vs. 90% efficient units?

    3) What exactly is "modulating capacity?"

    4) Is purchasing one of each an option or strictly two of the model I select?

  • Dale
    Dale Member Posts: 1,317
    boiler eff

    Sounds like you have an accurate heat loss on your building, one thing you may want to discuss further with your contractor is what water temp you will need. If you will need 160 or 180 or higher when it is cold the return temp may be too hot to condense so you won't get the extra percent effeciency. I would confirm what is the maximum return temp to get the added effeciency from condensation. If this is so your choice may be more complicated, perhaps the flue issue has you leaning toward the condensening versions. I could see a high end non condensing for the second stage and a condensing for the first stage used in the spring and fall.
  • ALH_4
    ALH_4 Member Posts: 1,790

    Efficiency of modulating condensing boilers is also based on the firing rate of the burner. During spring and fall the heat loss may be very low and the efficiency may be quite high even if the supply temperature is 160°-180°F. Outdoor reset could also be very valuable for limiting tenants' maximum room temperatures. Most mod/con's are equipped with outdoor reset standard.
  • Dave_4
    Dave_4 Member Posts: 1,405

    you only need one (1) btu wise

    consider 2 100'S OR 125'S WITH A TEKMAR . NO ERROR CODES
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